Bra Size Calculator
Compare two transparent bra sizing references from US Knix and UK Brastop using underbust and fullest-bust measurements.
Sizing hub
Bra Size
Use measurements as the starting point, then treat labeled sizes as a fit reference rather than a guarantee.
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Bra Size Chart
Compare common US, UK, and EU bra band references and cup starting points.
Bra Sister Sizes
Find nearby bra sister sizes that preserve roughly similar cup volume.
Bra Size Conversion Chart
Compare common US, UK, and EU bra band references before checking cup-system differences.
US to UK Bra Size
Compare US bra sizes with UK band references and account for cup-letter differences.
UK to US Bra Size
Compare UK bra sizes with US band references and cup-system differences.
US to EU Bra Size
Compare US bra band sizes with EU band references.
EU to US Bra Size
Compare EU bra band sizes with US band references.
Bra Size in Inches
Look up source-specific US Knix or UK Brastop bra fitting references from inch measurements.
Bra Measurement Chart & Size Reference
Measure underbust and bust for a practical bra-size starting point.
Use a full size, not only a cup letter
Cup volume changes with band size, and letter sequences differ between systems. Compare the band and cup together when converting or trying a sister size.
Fit checks come after the estimate
A calculated size is a starting point. Band support, cup containment, wire placement, strap comfort, and the brand’s own construction decide whether the bra actually fits.
Keep band, cup and measurement in the same comparison
Use measurements as the starting point, then treat labeled sizes as a fit reference rather than a guarantee. Do not convert only a cup letter or only a band number when the task involves a complete bra size.
Use underbust and bust as the stable measurements, then verify the full size with the brand because cup progression and fitting method can vary.
Two independent source methods, not one universal bra formula
Our bra calculator lets you choose Knix US (published underbust ranges and measured cup anchors) or Brastop UK (its own whole-inch band and cup difference guide). The two outputs are not claimed as interchangeable national labels.
The reference band chart on other bra pages illustrates a Wacoal Singapore-style centimeter-underbust convention; it should not be combined with either calculator method to manufacture a size. Fullest-bust and underbust measurements, bra shape and the intended product chart all matter.
Method & references
How this guidance is checked
These sources support the measurement method and help check real-world variation. They are not presented as one universal brand-size table.
- Bra Fit Calculator — Wacoal. Bra measurement cross-check using underbust and fullest-bust measurements and brand-specific fitting logic.
- Traditional Bra Size Guide — Underbust Bands and Full-Bust Anchors — Knix. Source-specific US bra fit reference: 11 published underbust intervals and 99 full-bust cup anchor cells; no inferred gaps.
- How to Measure Your Bra Size at Home — Brastop. UK whole-inch underbust band rounding and 1–15-inch measured bust-minus-underbust cup sequence A–K.
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